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Any particular reason for wanting metal midcaps?
Magpul's polymer midcaps (EMAGs for the L85) are strong and reliable. Admittedly at £20/mag, they aren't the cheapest magazines on the market, but the Magpul PTS midcaps are pretty damn good - as strong as the real magazines used in Afghanistan. Mine have been working for 2 years solid now. I've fallen on them, I've dropped them out of a 3rd floor window, no cracks or breaks. Just remember to go for the actual Magpul PTS ones, not the cheaper knock-offs. None of mine worked.
Plus, with the window showing the fake bullets, EMAGs look bloody awesome in an L85.
Not sure if they'll fit the F2000 though, I think the magazine well is too small.
But if you want metal mags, King Arms mid caps work well for me.